In a recording device using magnetic recording media such as hard disk drives and the like, even if a file delete command or data block delete command prepared in an operating system or the like is issued and the deletion processing is performed, as traces of data are left due to remaining magnetism, there is possibility that the information thought to have been deleted may be read by a third party. In order to prevent stealing of data and the like using remaining magnetism by a third party in a more reliable manner, a so-called shredding that repeats writing of data consisting of fixed values or random values in the same storage area needs to be performed.
As for shredding, PTL 1, for example, discloses that, in order to reliably prevent information leakage, the maximum number of overwriting and the number of overwriting of overwrite data on the disk cache in the server is managed, the maximum number of overwriting and the number of overwriting of overwrite data transmitted from the server on the controller cache in the storage subsystem is managed, and each of the addresses of the disk cache, the controller cache, and the hard disk drive storing a same file as the deletion target are managed so that the data as the erase target in the file as the erase target stored in each of the disk cache, the controller cache, and the hard disk drive is deleted in units of files.